Influence on Cardiac Autonomic Function of Repeated Exposures to Air-Conditioned Environment in Summer

Abstract

This study examined the effects of change in environmental temperature on the autonomic nervous system. Ten female subjects were exposed to two levels of temperature in different rooms. The temperature in Room 1 was set at 21 or 28°C while that in Room 2 was set at 35°C. Subjects were exposed to four different combinations of temperatures and periods: movement between Room 1 and Room 2 every 10 min (condition A) or 40 min (condition B) and between Room 1 and Room 2 every 10 min (condition C) or 40 min (condition D). At the condition A and B, Room 1 was set at 21°C , and it was set at 28°C at the condition C and D. The control group was kept in Room 1 maintained at a constant temperature of 26.5°C for 165 min (condition E). The experimental time totaled 165 min including the 5-min period immediately after the start of experiment. It was clarified that the invasion to the autonomic nervous system tended to be largest under condition B (moved every 40 minutes maintained at 21 and 35°C) by the results of Coefficient of Variation of R-R interval (CVR-R) and low-frequency (LF) and high-frequency (HF) components of ECG. Briefly, it was suggested that autonomic imbalance tends to occur when temperature difference is great or exposure to low temperature lasts long.